feat(nodes): add alpha mask to tensor invocation

invokeai/app/invocations/mask.py

@@ -1,7 +1,8 @@
+import numpy as np
 import torch
 
 from invokeai.app.invocations.baseinvocation import BaseInvocation, InvocationContext, invocation
-from invokeai.app.invocations.fields import InputField, TensorField, WithMetadata
+from invokeai.app.invocations.fields import ImageField, InputField, TensorField, WithMetadata
 from invokeai.app.invocations.primitives import MaskOutput
 
 
@@ -34,3 +35,25 @@ class RectangleMaskInvocation(BaseInvocation, WithMetadata):
             width=self.width,
             height=self.height,
         )
+
+
+@invocation(
+    "alpha_mask_to_tensor",
+    title="Alpha Mask to Tensor",
+    tags=["conditioning"],
+    category="conditioning",
+    version="1.0.0",
+)
+class AlphaMaskToTensorInvocation(BaseInvocation):
+    """Convert a mask image to a tensor. Opaque regions are 1 and transparent regions are 0."""
+
+    image: ImageField = InputField(description="The mask image to convert.")
+
+    def invoke(self, context: InvocationContext) -> MaskOutput:
+        image = context.images.get_pil(self.image.image_name)
+        mask = torch.zeros((1, image.height, image.width), dtype=torch.bool)
+        mask[0] = torch.tensor(np.array(image)[:, :, 3] > 0, dtype=torch.bool)
+
+        return MaskOutput(
+            mask=TensorField(tensor_name=context.tensors.save(mask)), height=image.height, width=image.width
+        )